Though Nintendo's iconic Super Mario franchise recently celebrated its 35th anniversary, some aspects of its titular character remain a mystery. It's not clear how old Mario is, for instance; the plumber has remained seemingly ageless for his entire career. In truth, Nintendo once detailed Mario's approximate age, and he's likely younger than many folks may think.
Mario made his grand entrance in 1981 as Jumpman in the Donkey Kong arcade game. Then, in 1983, Mario Bros. premiered, followed closely by 1985's Super Mario Bros., the start of a franchise that's gone on to launch over 200 titles to date. All games in the Super Mario universe take place at different points on the franchise's timeline, some even featuring a baby version of Mario, but that timeline is incredibly vague, as most Mario games have nothing to do with one another.
According to a 2005 Nintendo interview with Shigeru Miyamoto, creator of the Mario series, Mario was intentionally designed without many personality attributes, lest they inhibit ideas for future games. However, the team did decide Mario was in his mid-20s - roughly 24 to 25 years old. It may seem improbable for someone so young to have such a stable career and grow such a luxurious mustache, but Mario's relatively spry age does explain his agility and relentless endurance in trying to save Princess Peach.
What Mario's Current Age Is
Even with this in mind, it's not clear if Mario ages throughout the games or if he has remained in a perpetual state of being in his mid-20s. Though the aforementioned Baby Mario is a feature in several games, Mario's adult appearance hasn't changed, technology improvements notwithstanding. Mario being 24 to 25 throughout all of the franchise does align with his original design philosophy, creating a timeless character. If he doesn't age or change, there is no limit to what the character can be used for, and Nintendo can avoid the risk of retconning his backstory.
However, there have been a few clues suggesting Mario does age. A 1988 edition of Nintendo Power (via Twitter user Fantasy World 9) notes Mario's birthday is October 11, which indicates the plumber gets older every year. Additionally, in Super Smash Bros. Melee, close examination of Mario's trophy states he is 26 years old. Miyamoto (via shmuplations) also once called Mario a "weird old dude." If Mario does indeed age, assuming he was 24 to 25 for the 1985 launch of Super Mario Bros., he would now be 60 to 61 years old. Perhaps in a future Super Mario installment, fans will get to see Mario as the silver fox his age suggests.